I'm freshening up my 400SB Chevy with new rings and installing a set of used Vortec heads. Just for insurance, I am going to discard the old oil pump and install a new one. Here's my question...can I install a BB oil pump? If so, do I need a different length intermediate shaft? I like the idea of the big block pump having more gear teeth and producing slightly more oil volume without being much harder to turn than the small block pump....Do you gents agree?

Yeah, I'm a big fan of using the big block pump. It bumps the hot idle and lower RPM oil pressure up which these engines need if they're used hard at low and moderate RPMs or certainly if they are raced where frequent gear changes and high loadings are experienced which is the case on road track and short ovals.

The down side is the big block pump delivers a lot of oil you don't need in the RPM ranges from 3 to 6 thousand so the relief is dumping a lot of unused oil your spending a few horsepower to heat up and dump back in the pan. But I've found this a cost of providing better bearing protection in the lower revs.

Yes you need the shorter intermediate shaft and use a steel rather than plastic coupling.

With the Vortec, GM has had a lot of bottom end warranty issues related to insufficient oiling on hard working engines. I consider the BBC pump and using a 15W40 or 20W-40 oil to be significant insurance against these issues. Especially if you work the engine hard and live in a hot climate.